1. Field of the Invention
The present invention relates to a laminate body, a cross-linked product, and a molded member of elastomers. More specifically, it relates to a laminate body, a cross-linked product, and a molded member made of an acrylic elastomer and a fluorine-based elastomer.
2. Description of the Related Art
Acrylic elastomers and the cross-linked products thereof, which are superior in physical properties such as heat aging resistance, oil resistance, mechanical properties and compression set properties, have been widely used as materials used in automobile engine rooms such as hose members, seal members, and antivibration rubber members. Under the influence of increasing regulations on exhaust gas and increase of engine power, there is recently a demand for materials superior in heat aging resistance that can be used as such automobile members.
As a means for improving the heat aging resistance and thus for increasing the reliability of rubber parts, it may be effective for example to use a fluorine-based elastomer that is higher in durability than acrylic elastomers. However, because fluorine-based elastomers are lower in low-temperature resistance and more expensive than acrylic elastomers, it is needed to solve the problems above in order to apply them to materials for auto parts that demand low cost and high reliability simultaneously.
Thus, methods of using a fluorine-based elastomer in combination with another elastomer were proposed. It is possible to reduce the increase in material costs as much as possible and yet increase the durability substantially, for example, by forming only regions that may cause problems particularly in durability with a fluorine-based elastomer and the other regions with a conventional material.
An important requisite in properties when a laminate body is formed with multiple materials is the adhesiveness between layers of different materials. Low interlayer adhesion strength leads to decrease of reliability as a laminate body. In particular, because fluorine-based elastomers are less adhesive to other materials, it is quite important to improve the adhesion strength between the fluorine-based elastomer and the acrylic elastomer, to obtain a laminate body superior in durability cost-effectively.
Examples of the methods for improving the adhesiveness of fluorine-based elastomers include methods of treating the surface of a fluorine-based elastomer layer, with metal sodium solution (see, for example, Patent Document 1), by discharge treatment (see, for example, Patent Document 2), by plasma treatment (see, for example, Patent Document 3) and the like. Also proposed were laminate bodies that are improved in physical properties such as low-temperature embrittlement resistance and also in adhesiveness to non-fluorine rubber layers by blending a fluoroplastic resin having a particular structure to the fluorine rubber (see Patent Documents 4 and 5).
Patent Document 4 discloses that it is possible to improve the adhesiveness of a fluorine-based rubber to a non-fluorine-based rubber by using a polyol-based crosslinking agent for crosslinking the fluorine-based rubber or by adding an onium salt or an amine compound to the fluorine-based rubber. There is also reported a laminate body with the adhesiveness between the fluorine polymer layer and the non-fluorine rubber layer improved by addition of an adhesive compounding agent in a particular structure to the non-fluorine rubber layer (see Patent Document 6).